The New Sudoku Players' Forum

[Sudtyro2]

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 *-----------------------------------------------------------*
 | 67   *56    4     | 2     1     9     | 78    3    *568   |
 | 3    *569   17    | 4     8     57    | 2     157-9*56    |
 | 179   8     2     | 57    6     3     | 79    1579  4     |
 *-------------------+-------------------+-------------------|
 | 2     7     5     | 9     4     6     | 1     8     3     |
 | 8     1     6     | 57    3     57    | 4     2     9     |
 | 4     3     9     | 1     2     8     | 5     6     7     |
 *-------------------+-------------------+-------------------|
 | 679  @69    37    | 8     5     1     | 3679  4     2     |
 | 569   2     8     | 3     7     4     | 69    59    1     |
 | 157   4     137   | 6     9     2     | 378   57   #58    |
 *-----------------------------------------------------------*

OK, with all this new knowledge, let me now try an “externals” approach on AUR(56)r12c29 ala Ted's methodology.
Choose (6)r7c2 to cover the UR 6s in c2. The UR 5s in c2 are empty of externals.
Choose (5)r9c9 to cover the UR 5s in c9. The UR 6s in c9 are empty of externals.
I think that covers all 8 UR digits. Now form the SIS and aim, say, for Luke's elimination:

Code: Select all

    UR
    ||
(6)r7c2-(9)r7c2=(9)r2c2---(9)r2c8
    ||   
(5)r9c9-(5=9)r8c8---------(9)r2c8; ste

Or use the SIS to develop a single AIC:

Code: Select all

(9)r2c2=(9)r7c2-(6)r7c2=(5)r9c9-(5=9)r8c8 => r2c8<>9; ste

SteveC

[tlanglet]

Steve, both of your solutions are correct. However, it would help readers understand the third step of the AIC better by including the AUR reference such as:
(9)r2c2=(9)r7c2-AUR(56)r12c29[6r7c2=5r9c9]-(5=9)r8c8 => r2c8<>9; ste

Another possible solution using external inferences is:
AUR(56)r12c29[6r7c2=5r9c9]-(5=9)r8c8-9r23c8=9r3c7-(9=176)r3c1,r2c3,r1c1 => r1c2,r78c1<>6

Or how about mixed internal,9r2c2, & external,5r9c9, inferences
AUR(56)r12c29[9r2c2=5r9c9]-(5=9)r8c8 =>r2c8<>9

Ted

[David P Bird]

The expanded notation I gave before can be condensed in stages like this:

A: (8)r1c9 = (56)r1c29 -[UR]- (56)r2c29 = (9)r2c2
B: (8=56)r1c29 -[UR]- (56=9)r2c29
C: (8)r1c9 =[(56)UR:r12c29]= (9)r2c2

Which of B and C is shorter depends on whether the disruptors are internal or external.

There are two objectives for a notation:
1. To allow the reader to follow the logic used
2. To be succinct

The first of these is the dominant one, but it depends to some extent on how experienced the target reader is. It's quite a task for a novice to be able to follow the notation for a new method but, surprisingly, as soon as that has been accomplished, these difficulties are forgotten and the temptation is to make the notation as terse as possible. This may save the author time and paper but it is the reader who pays the price, particularly those novice lurkers we hope will soon join us.

Considering the effort that went into finding the solution, surely it's worth a few more seconds and a bit more screen space (it's not paper we're wasting) for one writer to make it easier for hopefully many readers. A writer who disregards this effectively sends the message that his time is more precious than anyone else's.

Thefisrtthingthattendstohappenisthatwhitespaceisremoved. This makes it more difficult to follow and, as the reader flicks from the notation to the grid and back again, it makes it difficult to return to the right place.

I've given sermons on this theme before but I feel I'm preaching to a hostile audience, so won't go on to detail other points. However I do suggest that people should remember their own initial difficulties when notating their solutions and before introducing yet another pet notation variation.

[eleven]

My 2 cents:
DP 56r12c29 => r1c2<>6, r2c9<>5, stte

Eleven, are you Uruguayan by any chance?

A pattern is a pattern is a pattern (and i don't call Denis' chains patterns).

Code: Select all

 A:ab ---a--- abX
   |          |
   a          b
   |          |
  abY ---b---B:ab
=> A<>b, B<>a


Any problem with that ?

[David P Bird]

Eleven, my previous post on notation relates here. Your solution quotes a Deadly Pattern but doesn't say why it produces the eliminations you derive from it, so it doesn't help much.

Now there are two possibilities:

1. You looked up this particular pattern in a pattern list to obtain these eliminations, in which case you should give its type number.
2. You analysed the pattern yourself to derive them, in which case you should show your logic.

However you did neither!

I'm pleased that we agree that Denis's chains aren't patterns, but we could argue forever about what the defining attributes of a pattern are! A more practical approach is the check if the pattern is named in a list of those that have been previously accepted by consensus.

As my response to you revealed, I've been following the World Cup which tainted my reply which I was trying to make humorous – I hope it didn't give offence.

[eleven]

No problem, i thought everybody would see the pattern - at least Danny had shown the strong links.

Go Costa Rica go - pura vida.

[DonM]

The first of these is the dominant one, but it depends to some extent on how experienced the target reader is. It's quite a task for a novice to be able to follow the notation for a new method but, surprisingly, as soon as that has been accomplished, these difficulties are forgotten and the temptation is to make the notation as terse as possible. This may save the author time and paper but it is the reader who pays the price, particularly those novice lurkers we hope will soon join us.

Considering the effort that went into finding the solution, surely it's worth a few more seconds and a bit more screen space (it's not paper we're wasting) for one writer to make it easier for hopefully many readers. A writer who disregards this effectively sends the message that his time is more precious than anyone else's.

Thefisrtthingthattendstohappenisthatwhitespaceisremoved. This makes it more difficult to follow and, as the reader flicks from the notation to the grid and back again, it makes it difficult to return to the right place.

I've given sermons on this theme before but I feel I'm preaching to a hostile audience, so won't go on to detail other points. However I do suggest that people should remember their own initial difficulties when notating their solutions and before introducing yet another pet notation variation.

Well said. I've also given sermons on the same theme.

[daj95376]

Code: Select all

 A:ab ---a--- abX
   |          |
   a          b
   |          |
  abY ---b---B:ab
=> A<>b, B<>a


Any problem with that ?

No problem ... BUT ... the pattern could be more general.

Code: Select all

  abW ---a--- abX
  |            |
  a            b
  |            |
  abY ---b--- abZ

=> abW<>b, abZ<>a


Now, it's 2x occurrences of this Mike Barker pattern.

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--- UR+4C/3SL: the links with equal labels share a node => "b" can be removed from "abZ"

abX-----abZ
     a   |
        a|
     b   |
abY-----abW


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